Wheel protection is an often debated subject in the robot combat world. Exposed wheels are much more likely to be damaged during a fight, but protecting them adds weight and sometimes can actually make the situation worse. Over the years I’ve had bots with most of the common wheel guard arrangements from nothing to fully surrounded by thick structural members. They’ve each got their pros and cons, so there’s no universal right answer to the question of “Which wheelguard is right for my bot?”

First up is the fully exposed option:
My 1lb robot Algos leaves its wheels completely open to the opposition. The big benefit of this arrangement is that with highly exposed wheels it’s difficult for your opponent to put you into a position where you don’t at least have a wheel on the ground. The downside is that you’ve got absolutely zero protection for your wheels. If you opt for fully exposed wheels be prepared to replace damaged wheels between fights and watch out for robots trying to take out your wheels.

Up next is minimalist guarding:
This arrangement is the lightweight option when it comes to wheel protection. This style of guard is typically designed to cover the expected angles of attack only to minimize the weight spent on protecting the wheels. This setup is often enough to avoid severe wheel damage during a fight, but with the minimalist nature of these guards there is the risk that a hard enough hit could warp the guards and either allow the weapon clear access to your wheels or cause the guards to interfere with your wheels potentially immobilizing the wheel.

The next step up in protection are wheel pods:
Wheel pods typically serve two purposes. Not only are they protecting the wheels from damage, but they’re also an integral element of the support structure for the drive system. Being a part of the support structure necessitates them being much more durable than the minimalist guards. Wheel pods don’t offer much more protection than the minimalist guards, but the increased strength requirements and tie-in with the rest of the chassis mean they’ll typically be able to handle moderate impacts well. Integrating wheel protection with overall chassis structure is a more efficient use of weight, but there is a risk that a bent section of frame could result in jammed wheels.

The top external wheel setup is the fully wrapped guard:
With this setup there is no unprotected path to the wheel. With adequate space between your wheels and a fully wrapped guard it will take significant effort for the opposing robot to reach your wheels. If the guard can take the blows your wheels will be safe in most circumstances with this sort of guard. The major downside to this style when compared to something like the minimalist guards is that for the same weight you won’t be able to get nearly the level of protection in the most critical areas. This type of guarding is a good all around option but is lacking compared to other options when it comes to defending any specific location.

Finally, the most protected setup is the internal wheel:
At the top of the pile you’ve got this setup. The wheels are completely contained within the chassis with only a small portion of them exposed where they contact the combat surface. With internal wheels you’ve got the most protected, but most limited setup. Special consideration also needs to be given to the components in the robot near the wheels to ensure they don’t come into contact with the wheels after a heavy impact. The level of protection is unmatched by the other options. By the time your opponent has a clear shot on your wheels you’ve already likely sustained substantial damage. The main downside of this setup is that your wheels will likely have a very limited number of positions where they are in contact with the ground, making it easier to get stuck or high centered.

As I said at the start, there’s really no right answer. Everyone’s got a style that works for them. I tend to lean toward minimal protection for several reasons:

Improved maneuverability. It might be subtle, but occasionally a bit of extra agility makes the difference.

Lighter weight. Less weight in wheel protection is more weight that can be put elsewhere.

Strategy. This is more hypothesis than fact, but I take the view that if you’ve got exposed wheels they become a primary target for your opponent. I take the view that if you know the target of your opponent you’re better able to defend it and in close fights this can be the strategic advantage that tips things in your favor.

This weeks post is going to take a bit of a different direction from the last few. Instead of talking about broad topics and skill building it will be on a recent project. In this case, it’s on the repairs and upgrades I’ve been making to an insect class combat arena.

The arena itself was originally used for Robot Battles events and was retired after Dragon Con in 2011. After that, it sat in a garage for a few years until the owner offered it up free of charge to whoever was willing to give him a bit of space back. I took him up on the offer and we got the arena moved from his garage to mine.

After a dusting and de-cobwebing the arena was ready for work to being. First up was a lot of patching on the floor:

A few hours of wood filler and sanding and the floor was relatively flat and ready for paint. I decided to go with a basic white paint as that’ll help the robots show up well on video and it’s going to get battered eventually and white will make for easy touch-ups.

With the painting done it was time for a test fit of a few critical components, namely the legs and lexan. A bit of wrestling with it and the arena was set up and ready for a bit of testing. I tossed Algos into the box and took it for a test drive. Overall, it worked quite well. Traction seemed decent and the wedge on Algos wasn’t finding any places to dig in.

The final bit of painting was up next. I was able to get an acrylic template for the starting squares cut at Freeside Atlanta. (https://wiki.freesideatlanta.org)

Some masking tape, paper, and a bit of time with the spray paint and the new starting circles were added. I decided to keep with the red/blue scheme the arena started with.

The observant reader will notice a large hole to one side of the floor. That hole is for the arena hazard. Obviously I couldn’t leave the hole open for combat, so the next order of business was to figure out why the arena hazard wasn’t working properly. Some experimentation in the shop revealed that the main problem was that the solenoids used to power the flipping plate could overextend themselves and jam, preventing the hazard from firing properly. To solve this I 3D printed four stop-blocks that were then glued into place using Goop.

A bit of testing later and I was convinced that the flipper was working well enough. With the hazard reasonably fixed it got a quick orange and black paint job to match the arena walls.

If you’re wondering how it works, there’s a contact switch in the flipper plate itself that’ll trigger the solenoids when it’s depressed. The solenoids are installed backwards and slam their rams into an angle bracket that pushes the flipper plate up, hopefully sending the offending robot into the air. In testing it was capable of sending a 1lb bot from the wall to the middle of the arena.

This left one major detail that still needed to be addressed, the pushouts. The openings in the wall are meant to allow robots to be eliminated by their opponent shoving them off of the combat surface. I wanted to create a pit that would be reasonably light, durable, and securely attached to the arena frame. After a bit of messing around with ideas I settled on steel framed baskets with an expanded metal skin and a thick foam lining.

The whole thing is made from steel that has been cut, bent, and welded into shape. The main structure is 1/4″ steel rod which slots into a pair of holes at the edges of each pushout. This attachment method allows the pits to be quickly dropped into place for easy setup and minimal risk of a robot escapee.

As with many things, the final detail was the paint. Each pit was hand made to match hand drilled holes, and because of that, they’re not identical. The pits were color coded to match the side of the arena that they fit to make things easier during events.

The last bit of work wasn’t much in the way of actual work. One of the two halogen bulbs had been destroyed at an event and was never replaced. I spent a bit of time looking around and found an LED replacement bulb and swapped in a set of them in the hopes that they’ll be more durable and be less of a safety risk since they should run a fair bit cooler.

At this point the arena’s in good enough shape for its first event, which is a good thing as it’ll be getting used May 9th at Freeside Atlanta for the first Freeside Robot Street Fight. (http://sparc.tools/forum/index.php?topic=87.0)

There is more work planned for the arena. The next major addition will be the creation of another hazard that can be used at events.